This present invention generally relates to a propeller blade constructed from a fiber-reinforced material, and more particularly to an arrangement for protecting the structural integrity of a plastic propeller blade against damage from lightning strikes. Propeller blades are among aircraft components most frequently struck by lightning. Carbon fiber-reinforced plastic materials are especially sensitive to lightning damage due to their partial electrical conductivity because the fiber is conductive while the plastic matrix is insulating. Carbon fiber blades are also more conductive than Kevlar blades and are therefore harder to protect. Typically, this protection is provided by a surface film of lightning strike protective material (e.g., cooper or aluminum) which is laid on the outer surface of the composite blade. This type of construction; however, adds complexity and weight to the propeller design. Moreover, with conductive materials, such as with Carbon fiber, the desired blade protection is difficult to achieve due to the possibility of “puncture” of the protective surface into the carbon material. This puncture allows current flow into the carbon material which will result in damage to the blade. This is the primary reason for the high dielectric glass that covers the carbon fiber material in this type of protection scheme and if it is not strong enough, then the voltage created by the spark gap will break down the dielectric and arc to the carbon fiber, causing damage to the blade. This protection scheme is also very susceptible to manufacturing issues and therefore the reliability of the design is very suspect.
Therefore, it is an object of the present invention to provide a propeller blade constructed from a composite material with lightning protection that does not require lightning protection material incorporated into the material lay-up itself.
For the foregoing reasons, there is a need for a propeller system capable of being fabricated into a configuration that will provide high performance aerodynamic characteristics with lightweight, high structural integrity and lightening protection in a single package.